Grab co-authorship; added list of things that will/may change; added

alternative implementation.

pep-0237.txt

@@ -1,7 +1,7 @@
 PEP: 237
 Title: Unifying Long Integers and Integers
 Version: $Revision$
-Author: pep@zadka.site.co.il (Moshe Zadka)
+Author: pep@zadka.site.co.il (Moshe Zadka), guido@python.org (Guido van Rossum)
 Status: Draft
 Type: Standards Track
 Created: 11-Mar-2001
@@ -18,6 +18,10 @@ Abstract
     types from the perspective of both the Python interpreter and the
     C API.
 
+    Note from second author: this PEP requires more thought about
+    implementation details.  I've started to make a list of semantic
+    differences but I doubt it's complete.
+
 
 Rationale
 
@@ -72,9 +76,39 @@ Overflows
     aid, and has no guaranteed semantics.
 
 
+Semantic Differences
+
+    The following operations have (usually subtly) different semantics
+    for short and for long integers, and one will have to change
+    somehow.  This is intended to be an exhaustive list; if you know
+    of anything else that might change, please write the author.
+
+    - Currently, all arithmetic operators on short ints except <<
+      raise OverflowError if the result cannot be represented as a
+      short int.  This will change (of course).
+
+    - Currently x<<n can lose bits for short ints.  No more.
+
+    - Currently, hex and oct literals for for short ints may specify
+      negative values; for example 0xffffffff == -1 on a 32-bint
+      machine.  No more; this will equal 2**32-1.
+
+    - Currently, repr() of a long int returns a string ending in 'L'
+      while repr() of a short int doesn't.  The 'L' will be dropped.
+
+    - Currently, an operation with long operands will never return a
+      short int.  This may change.
+
+    - Currently, type(x) may reveal the difference between short and
+      long ints.  This may or may not change (see Implementation
+      below).
+
+
 Implementation
 
-    The PyInt type's slot for a C long will be turned into a 
+    There are two alternative implementations to choose from.
+
+    1. The PyInt type's slot for a C long will be turned into a 
 
         union {
             long i;
@@ -84,10 +118,13 @@ Implementation
             } bignum;
         };
 
-    Only the n-1 lower bits of the long have any meaning; the top bit
+       Only the n-1 lower bits of the long have any meaning; the top bit
-    is always set.  This distinguishes the union.  All PyInt functions
+       is always set.  This distinguishes the union.  All PyInt functions
-    will check this bit before deciding which types of operations to
+       will check this bit before deciding which types of operations to
-    use.
+       use.
+
+    2. The existing short and long int types remain, but the short int
+       returns a long int instead of raising OverflowError.
 
 
 Jython Issues